Senia read law at the University of Hong Kong and obtained her LLM (Specialism in Human Rights) (Distinction) at the London School of Economics and Political Science. Senia called to the Bar in 2014 and has a broad, predominantly civil, practice, with particular focus on judicial review. She is currently involved in a number of judicial review cases against the Chief Executive of the HKSAR, the Secretary for Justice, the Clerk to the Legislative Council, the Legislative Council Commission, the Hong Kong Housing Authority and the Appeal Panel (Housing). She also represented the Coalition of Victims in the Commission of Inquiry into Excess Lead Found in Drinking Water in 2015-2016.

Senia has been teaching at the Faculty of Law of the University of Hong Kong since 2015, and has taught undergraduate students Constitutional Law, Administrative Law and Legal Systems. She is also an elected member of the Chief Executive Election Committee (Legal Subsector) and a member of the Standing Committee on Civic Education of the Hong Kong Bar Association.